Thermoplastic
Polycarbonate
Transparent, and the toughest common engineering thermoplastic.
Published values for unfilled grades at 23 °C unless stated. Confirm against the supplier datasheet for the grade you specify.
What it is
Polycarbonate is the material you specify when a part has to survive being dropped, hit, or loaded near its limit without shattering. Notched Izod impact is roughly ten times that of acrylic, and it fails by yielding rather than cracking.
It is optically clear, holds tolerance through a wide temperature range, and is rated for continuous use around 115–125 °C. The trade-off is chemical sensitivity: many solvents, alkalis, and some cleaning agents cause stress cracking.
Where it is used
- Safety guards, machine windows, and light covers
- Medical device housings that face autoclave or chemical wipe-down
- Automotive lighting lenses and light pipes
- Electrical enclosures and connector bodies
- Structural prototypes that have to be tested, not just looked at
Processing notes
Drying is not optional. Below 0.02 % moisture, typically 4 hours at 120 °C. Wet PC hydrolyses in the barrel and loses most of its impact strength permanently.
Melt 280–320 °C, mold 80–110 °C. It is a stiff-flowing material; expect higher injection pressure and larger gates than ABS.
Anneal thick or optical parts to relieve molded-in stress, otherwise stress cracking appears weeks later in service.
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Design notes
Generous radii everywhere. PC is notch sensitive, and a sharp internal corner will start the crack that impact then finishes.
Wall 2.0–3.5 mm for structural parts. Uniformity matters more than in ABS because of the higher molding stress.
Avoid molded-in threads and press fits that hold the part in tension; combined tensile stress and solvent exposure is the classic failure mode.
Grades and variants
- Optical grade, low haze, tight refractive control
- Glass filled (10–30 %), stiffer and more dimensionally stable, no longer transparent
- Flame retardant V-0, for electrical and rail applications
- Medical grade with USP Class VI or ISO 10993 documentation
- UV stabilised, for outdoor glazing and lighting
Alternatives
If Polycarbonate is not the right answer
Specifying this material?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.